1. Field of the Invention
The subject of the invention is a grapple harvester which is equipped with a felling and cutting device, a feeder and delimbing devices.
2. Description of Related Art
As part of forest management the young trees should be thinned at various stages of growth. The harvesting of small, first thinning trees is, however, dependent on the cost of mechanised harvesting of the trees, and is not carried out if it is too expensive. Attempts to solve this problem include the harvesting and processing of several trees simultaneously. There are various bulk handling devices available with which trees can be gathered together into one bundle. An example of this type of device is presented in patent publication FI 88853. Similarly, there are grapple harvesters that can process several trees simultaneously with the kind of equipment presented in patent publication FI 97340. A problem, however, with this kind of harvester is that the tree can slip onto or past the cutting device when a new tree is taken into the harvester grapple. The tree contacting the cutting device is then cut again, resulting in short lengths being left in the forest.
Bulk handling devices are expensive specialist machinery designed for specific tasks and they are difficult to use and employ all year round. Although various contributing factors exist in other equipment, flexibility in forest operations is dependent on the bulk handling characteristics of the device not interfering with the normal handling of individual trees.
One aspect of this invention is to introduce a grapple harvester with which the problems associated with present devices can be resolved. Another aspect of this invention is to speed up and facilitate the process of handling several trees simultaneously. Yet another aspect of this invention is to introduce a grapple harvester which can be used as a bulk handling device whilst, at the same time, retaining the grapple harvester normal grab such that the same unit is suited as it stands for use both in first thinning work and in final felling.
The purpose of the invention is achieved with a grapple harvester equipped with a bulk handling device which is arranged to grip together several trees, which are usually gathered one by one and, preferably, whilst in the vertical position, for cutting by the grapple harvester. Each tree is gripped by the bulk handling device while the next tree is gripped by normal equipment of the grapple harvester, so that during all stages of the work the grip on the trees is retained alternately by the collector gripping devices and the feeder and trimming devices of the harvester head. In this way these cannot slip onto or past the guide bar. When several trees can be gathered in the vertical position with the equipment, it can xe2x80x9cbumpxe2x80x9d close to the next tree to be gripped so that the equipment functions in a stable manner. An advantage of the invention is that the bulk handling device is an attachment to the grapple harvester and does not interfere with the normal felling work of the grapple harvester, for example, on the final felling site, where the harvester head can be used as a normal grab.
In an advantageous arrangement of the invention, the bulk handling device is attached to the frame as an extension to the tilting arm, so distance from the felling and cutting devices and includes one or more gripping devices. In this way the bulk handling device, being sufficiently distant the other gripping and feeder devices, helps in directing the tree bundle parallel with the delimbing line so that the blades do not dig into the and delimbing is made easier. In some arrangements, the bulk handling equipment can be attached, for example, to the tilting arm or to some other part.
According to aspects of the invention, the bulk handling device advantageously includes dipping devices which hold the cut and gathered trees in tight grip and which can also gather new trees into their grip. When a suitable quantity of trees has been gathered in this way the tilting arm is released and, at the same time, the gripping devices open and let the tree bundle fall freely. The gathering gripping devices remain turned against the tilting arm when the are dropped into the threshing position, nor do they, in these circumstances, interfere with the delimbing.
In the bulk handling device according to the invention the gripping devices are equipped with separate extensions which are bent inwards. With these extensions the trees can be locked effectively into the bulk handling device.